At least some of this story appears in the novels, but the manga does a good job of showing the early life of Tatsuya and Miyuki in great detail. Readers might feel a little disappointed at how Miyuki is cast early in their lives as a heartless emotionless monster who treats Tatsuya as horribly as his own mother. However you will also be treated to how and why Miyuki changes her opinion of him and what might be called the 'final straw' the moment when all her prejudices are destroyed in an instant. Until it gets to that point, there is a fairly gradual build up in how Miyuki is constantly forced to wonder why her brother is prejudiced against by her family as over time she witnesses things in him that force her to question the legitimacy of her family's claims that he is a useless disposable tool and not worth treating like a brother. The best and most suprising character in the entire story however is Tatsuya's adopted mother, Honami who is technically his mother's bodyguard, a manufactured mage, and herself treated like little more than a tool. Tatsuya displays during this story something he is not supposed to have at all and that was supposed to have been destroyed when he was a small child by his mother and aunt's magical experimentations and operations on him. If that is so, then how does he show emotion so strong it causes him to have an out of control emotional fit? When you read the full story you will find out much more about him and his 'real' mother. Honami was really the only mother he actually ever had because she treated him with love and like her own child far far more than his own heartless beast of a mother ever did. This is the story the novels nor the anime ever get into quite so deeply and reveals hidden truths about Tatsuya's past, Miyuki's sudden change of heart, and the relationship with the woman who was more a mother and family to him than even Miyuki herself ever was. You will truly see the heartbreaking story of how Tatsuya came to be what he is and how unfairly he was mistreated as a child. You will see the slow gradual build up of how he changed the view of some of those who thought wrong about him and the pivotal moment that broke everything away.
You will also see how and when he began his life in the military and how he met the people that would truly give his life purpose and his own self worth and identity apart from that of a mere tool. This is a great story and essential for any fan of the Irregular at Magic High School to truly understand the full story of the Shiba family.